Components With Dual Function Law and Legal Definition

According to 26 CFR 1.23-2 (Title 26, Internal Revenue; Chapter I, Internal Revenue Service, Department of the Treasury; Subchapter A, Income Tax; Part 1, Income Taxes; Normal Taxes and Surtaxes; Determination of Tax Liability; Changes in Rates During a Taxable Year), “to the extent that a passive or active solar system utilizes portions of the structure of a residence, only the materials and components whose sole purpose is to transmit or use solar radiation (and labor costs associated with installing such materials and components) are included within the term "solar energy property". Accordingly, materials and components that serve a dual purpose, e.g., they have a significant structural function or are structural components of the dwelling (and labor costs associated with installing such materials and components) are not included within the term "solar energy property". For example, roof ponds that form part of a roof (including additional structural components to support the roof), windows (including clerestories and skylights), and greenhouses do not qualify as solar energy property. However, with respect to expenditures made after December 31, 1979, a solar collector panel installed as a roof or portion thereof (including additional structural components to support the roof attributable to the collector) does not fail to qualify as solar energy property solely because it constitutes a structural component of the dwelling on which it is installed. For this purpose, the term "solar collector panel" does not include a skylight or other type of window. In the case of a trombe wall (a south facing wall composed of a mass wall and exterior glazing), the mass wall (and labor costs associated with installing the mass wall) will not qualify. However, the exterior (non-window) glazing will qualify. Any shading, venting and heat distribution mechanisms or storage systems that do not have a dual function will also qualify.”